Continuous polymerization of a conjugated diene with a monovinyl aromatic compound in the production of random copolymers by organolithium initiation in solution polymerization systems offers real production advantages. Polymerization procedures operated as a continuous process rather than as a batch process provide for the more economic production and more uniform compositions. Process variables can be readily adjusted in a continuous operation so as to optimize operations for a given polymerization recipe. Minor adjustments of monomer feed rates, initiator rates, randomizer rates, temperature control, pressure control, solvent usage, all can be readily made in a continuous process, in effect "fine tuning" so as to maintain relatively consistently a product with optimum properties.
The equipment employed comprises at least two reactor means operated as a reactor series or train through which the polymerization reaction mixture flows in its progress of polymerization from initiation to final termination. Unfortunately, such a continuous solution polymerization process has the disadvantage of a tendency toward fouling, especially in the first reactor means in the chain through a buildup of polymeric materials on the surfaces of the reactor means in contact with the reactants, fouling of heat transfer surfaces, stirring or circulation means, and the like, often ending prematurely a continuous polymerization run. It is readily apparent that the longer that equipment can be operated on a continuous basis, the more economical the overall results. Having to stop the entire process, clean the equipment, and then start up all over again, means, again, attendant startup problems and necessity to again fine tune the operation.